The invention relates to radio distance measuring equipment, comprising means for linear frequency modulation, with a frequency deviation .DELTA.F, of a carrier wave having a mean frequency Fo produced by a carrier wave source. The equipment also includes means for emitting the modulated carrier wave, means for mixing carrier wave energy reflected by an object with a part of the emitted wave in order to form a beat signal having a beat frequency fb, and control means for keeping the beat frequency fb constant by varying of the period of the frequency modulation.
In known radio distance measuring equipment as described in the technical journal "L'Onde Electronique," June 1979, pages 615-621, precision is realized by calibrating the frequency deviation .DELTA.F at regular intervals by means of an internal standard delay line which periodically takes the place of the distance to be measured, and by controlling the beat frequency fb.